Coated composite refractory body



2 SHEETS-SHEET l C. G. GOETZEL.

COATED COMPOSITE REFRACTORY BODY Sept. 30, 1952 Filed May 19, 1949 INVENTOR. 62/906 G4 6057-254 mmmvsrs S p 1952 c. G. GOETZEL 2,612,442

COATED COMPOSITE REFRACTORY BODY 2 SHEETS-SHEET 2 Filed May 19, 1949 46 36 INVENTOR. F R 49 62am 61 Gain-25L HTTDAWEYS Patented Sept. 30, 1952 "COATED. COMPOSITE REFRACTORY" BODY QClaus G.: .Goetzel, Yonkers, N. =.Y.,:. assignon to -Sintercast Corporation of America, New: York, N. Y., a corporation of New York "Application May 19, 1949, SerialNo. 94,092

. 5 Claims. 1

This invention relates to 'prote'ctive surfaces on structural components useful for high' temperature and oxidizing or corrosive atmosphere conditions, and particularly to a protective surface 'fonrefractory metal components, especial-1y composite body materials.

Components suitable for use as buckets, blades, valves;nozzles, andlthe like; in gas-or steam turbines, jet engines, and -devicesihavingsimilar temperature and atmosphere conditions have been difficult to provide. l Such components must have certain desirable-physical characteristics so that=- the= component will withstand" the stresses by alloyingithe:individualpcarbides; such as: titanium r carbide with tungsten carbide, but: the order of the improvement istinsuffi'cient 3011117130.- tical purposes especially under: conditions: of :use as exacting as components for" gas; turbines .and

. jet engines.

involved-= at the thigh temperature of operation a and will notdeteriorate in the oxidizing or corrosive conditions existent. Y The elements must have "high *hot tensile *strength, hot *fa-tigue strength, and :high resistance to creep'atelevated temperatures. 1 Materials containing: stable compounds such as borides, silicidesg and nitrides, of

the. refractory metals tungsten; molybdenum, titanium; 1 zirconium, chromium; etc., or suchstable oxides: as those of the metals aluminum; magneslum, -zirconium, silicon, or berylliumporc such stable carbides as those of-the non=metalssilicon or. boron; are desirable from'a corrosion and oxidationiresistance. standpoint. The materials just mentioned: containing 1these compounds, 1. however,:are: generallyrinferior Lin -their combination ofxphysical properties; such as cohesive strength, resistance tozmechanical'r and thermal shock; and heat rconductivity. Compounds based on r the combination.of'carbonwithithe refractory-metals tungsten, molybdenum, titanium, zirconiurhytantalum... c'olumbium, etc:,: possess :better: sets. of physical :1. properties, particularly, :1 resistance A a to thermal and .mechazucal shock: and cohesive strength. .xThisris especially. trueswhenrthey are alloyed with :certain metallichbinders 'suchias cohalt orcxnickel. lOne:of the difficulties is that. the aforementioned 1 refractory metal 1.; carbides. :base materials: are not stable: as far: as oxidation." and corrosion resistance'iat high-temperatures.

.. As an 3 example, titanium r carbide, .zirconium carbide; molybdenum carbide, or a tungsten car- I above 1500 F. Some improvementisattained Iron and. steel have been. surfacectitreatedrlby coating the :same by; straightzelectrodeposition or plating: spraying, or: byithe: so-called' fimpregenation? treatments involving diffusion and'izmetal atom .exchange'mechanisms :between (the Ida-1 posited metal. and the base metal. 'I hedepositing 10f the" surface metal in 1; the I impregnation treatments can be through immersion of rthe componentin a saltibath,:immersion 11'11 aipowder pack containing the surfacingxmaterialsi orsby.

exposing the body to a gas'streamrcontaining the surfacing metal in 1 the" form of Ia; volatile compound, such. as a. halide; or :plurality of halides.

The aforementioned surfacing treatments especially of the impregnationftype,:arezmost effectively applied .to thepure metals Which'fo'rm complete orxsubstantially 'complete solid solutions in any portion of the binarysystem because of the high diffusion rates involved. An example is iron, or' molybdenum, or tungstenywhenchromium is used I as asurfacing metal. "When several phases" orcompounds are formed by alloying of the surfacing and the base metal; 'the 'cliffusion rates are: slowed so that=the impregna' tion on diffusion treatment requireshigher' temperatures, more times, and a higher concentration of the surfacing metal I ormaterial in the compound .which is in contact with-thebody'to be :protected. This is 'true, for 'examplaflzwhenthe. base. metal is; nickel or', cobalt .and: the neposited metal is chromium.

The impregnation treatment "is 1 still moreiiimpeded and incertain uses wholly ineffective-if. the base metal contains a compound such as a carbide as a: majorconstituent, for example,

eutectoid or hyper-eutectoid steel, or cast iron.

process to continue indefinitely while the e1e-,

result. the concentration of the surfacing mate- I rial would progressively become diluted at the surface and would become insufficient to withstand external corrosive attacks. As an example of this effect, a body of molybdenum which has been surface impregnated with chromium through deposition of chromous iodide vapors would withstand the"oxidizing atmosphere of still air at 1800 F. for the short time of only 5 to minutes. A similar body of pure tungsten identical- 7 this must be done prior to the sintering operaly treated would Withstand exposure to air at such a temperature for only 20 to 3 0 minutes. 7 A body consisting mostly of a refractory carbide,

such as tungsten carbide or titanium carbide ce-' mented with a relatively small portion of cobalt or nickel (for example, 3 to 13%), would practically entirely prevent migration of atoms of chromium or other surfacing elements into the structure and of tungsten or titanium toward the surface free to combine with halogen. Thus, the mechanismof atom exchange would be sub,- stantially. inhibited by the carbide structure so that the deposited surface metal would merely bein theiform of a plate without a strong bonding or merger with the base material. For this reason, differences in the coefficient of expansion of the. base material and the depositedmetal would tend to cause a spalling off of the deposited surface material during heating or cooling of the body and an immediate break-down of the protection ofthe base material would follow.

, One of the principal objects of the invention is.;to -provide a method for making an article which will have the desired high physical characteristicsat high temperature under, oxidizing and corrosive conditions of operation;-

' One of .thefeatures of the present invention is to overcome the. prior; defects by the use of an intermediate metallic phase between the refractory carbide core structureand thedeposited and diffusionalloyed surface metal casing, said in-. termediate phase serving. to provide a medium wherein armerger'can take place with the outside caslngh f .Such an arrangement will permit the metal atom or other transfer exchange mechanism between the intermediate phase and the surface casingto. take place unhindered for a limited depth before the barrier against further inward diffusion of, thedepositedsurface metal becomes effective. Preferably, the diffusion takes place sojthat the surface metalwill penetratethrough theintermediate phaseand to a limited extent into the binder in the refractory carbide core structure. It also provides a buffer or cushionlike intermediate metallic layer of great ductility whichwill absorb the stresses caused by differences in the expansion of the cemented carbide base material and the deposited surface metal or stable oxide compound formed thereof. t is preferable, though not absolutely essential, that the'intermediate metallic surfacinglayeror phase should be of the same metal or materials as the metal or alloy used as the binder for the car-- such as carbides, in conjunction with the skeleton or base carbides. The intermediate phase may be deposited or formed on the component in various manners,

such as by painting or spraying. Also, if could be formed thereon in an infiltration step of the skeleton, if such is used, or in a hot pressing operation wherein. manipulations can be made so that a layer of the binder metal will-completely encase the component. If the intermediate phase is painted or sprayed on the component tionas will be explained hereafter. One of the main essentials is" that the intermediate phase film should be uniform on all of the surfaces of the component.

Following the placement of the intermediate phase on the component, surfacing impregnation of the component is carried out. Surface impregnation with the chemically stable heat oxilation and corrsion resistant element or materials may be theorized to-be based on a metal-atom and the intermediate phase.

allow for the desirable metal atom exchange process.

metal into the binder in the base material.

The surface deposited metalmay be placed on the intermediate phase in various manners, such as, by deposition. from the vapor phase, salt bath,

or powder pack methods. Thevapor phase dean impregnated pack arrangement wherein the component is placed in a pack. of suitablematee;

rial and the gas passed therethrough, the gas-reacting with the material inthepack to formthe. vapor phase for deposition on-thesurfaces of the.

Similarly, the gas" may .be passed. 1 over or through the surfacing metal whilethe metal is in liquid state so as to carry. along the,

The surfacemetal also may be; deposited by means of conventional powder pack;

component.

metal, vapors.

and salt bath methods. r

It is also desirable to. consider surface Ina-J terial from the view point of stabilityof either the pure metal or an oxidic compound formed thereof when exposed to the oxidizingv atmosphere of the high. temperature of the service of the component. .As will be explained hereaf'ter;= it is more advantageous to employ alloys which: are selected so that one constituent forms stable .Also,,=a single metal may be complex oxides. used which formsdirectly a mechanicallystable oxide at high temperatures. 1 For deposition from.

the vapor phase,.the preferred metals are those of high vapor pressure and those which. form.

. the following description and drawings whichare:

merely exemplary.

At the same time, the. intermediate phase preferably; should not be. so thiclr as prevent the limited penetrationof the surfacing q mgurec isa-sectional view of another. form of apparatus for depositing a surface material on a-oomponent.

Figure 5 is basedona-photomicrograph LX250) of aspecimen-made in' accordance withithe presentinvention. i

I Figure 6' is'an l enlargedv diagrammatic: representation-of a:.surface =se otion of arcomponent made inaccordance with-'the-"presenti invention. As -previously mentioned, the invention is especiallyadapted for .use with a cementedrefractory metal carbide composite-body. i

The cemented --refractory metal carbide component can -be made in various ways. For example, the metalpowdersmaybe mixed-sintered and pressed as is wellknown in theart. Also, the

. 6 economic :and industrialxrconditions, orecn it fll ultimatefphysical properties'desirabler .filhesei to a: certain extent ::are afiectedrby i the particular method of producingthecarbide'body.. I

carbide-base metal may beformed into a-skeleton having pores therethrougn-said skeleton thereafter being infiltrated-with the cementing metal or alloy of lower melting point than theskeleton. Aspreviously set forth, the refractory metal base carbide-materials may be-such as titanium carbid'eyzirconium carbide; molybdenum carbide, or

tungsten: carbide, F refractory metal 1 meaning a metal or material having a meltin'g point above iron which is about '2800" F. Various combinations of these carbidesalso may beused as desiredi The binder or cementing metal or alloy may be onethatis suitableior the purpose, and selected from the 6th to- 8th group and eth series (3rd period) of "the periodic table. As an-example,"='nickel or cobalt o'r-a11oys thereof can be used-as will'be set forth-hereafter. 1 The preferred refractory metal base carbide is titanium carbide for the major phaseof'the base material because titaniumi ca'rbide has'aunique set of' properties for the-purposeherein', suchas alow specific-gravity (4.2) and'highhardness *(Vickers Diamond Pyra'mid No: 3200 at'room temperature) It also has a limited but significant afiinity' -and solubility toward certain of the binder metals such as cobalt; nickel, chromium or alloys thereof. As an' example, ifcombined with cobalt in-a weight ratio of 8'parts titanium carbidey-andz parts-cobalt, a hardness of 'Rockwell A--92, combined 1 with a transverse rupture strengtltof 200,000pas. i. at room temperature and-up'to 100,000 p.=s. i. at 1800 F. is attained.

Similar values are possible with zirconium carbide having nickel or cobalt as the" binder metal. A-lso, titanium carbide is a more stable compound at elevated temperatures than most of theother carbides anddoes not decompose and liberate carbon which forms all-oyswith certain of the metals used-as-a binder and/or the intermediate layer, for example, nickel. f

The composite body whichis to be surface treated can be made in various manners such as: (1) Cold pressing,presintering, and sintering; (2) Hot pressing; (3) Infiltration of the binder metal into the presintered or sintered carbide skeleton.

Any of thesemethods are useable for thisinvention, the choice depending upon prevailing Inthe infiltration processglthe-skeleton 'may;l.be infiltrated with the binder: metaliin variousemanners. .As an example the skeleton may the formed in a mold under pressureyeither dynamic or static, or i a :combination 'thereof, following which the skeleton maybe sintered' 'and removed from. the: mold or the mold may' betransferred to: the infiltration zone. The infiltration: may

be" carrie'dtout" by capillary action, 'undervpres 1 sureunder vacuum or invarious mannersr various 'izheat treatments may be: giventhein filtrated skeleton after infiltration.

If ordinary cold pressing, presintering and sintering, methods of. producing I the cemented carbide bodyare employed; theintermediatesurface phase or casing can be applied in various ways; The pressed or green cementedcarbide compact can'have the metal paintedlthereon using an organic vehicle -such as gollqdion V lacquers. 7 Also the presin'tered cemented carbide compact can have the intermediate metal phase painted thereon.

This intermediate metal phase, for example, can be cobalt or nickel corresponding to the binder material of the cemented carbidecompact; It also ispossible to spray the intermediate phase material on the pressed green cemerited: carbide compact, or to spray'it on the presintered cemented carbide compact. spraying is used, to apply the intermediate phase, the metal or alloy should be in conventional powderform, such as Schori process powder. In order to have improved surface adherence of the sprayed-on articles to the comparatively hard surfaces involved or encountered in the-presintered compact,:an alloy with adistinct difference between the solidus and-liquidus thereof can be .used to advantage which can besprayed on in the mushystate. An example of this would bean alloy of nickel and chromium in the ratio The :intermediate surface layer applled pa'intingor spraying onto-the cemented carbide compactis diffused an'd/ orfused with the-binder phase of the cemented carbide body in the'subsequent sintering operation. i r v Itis essential that the painting or spraying be accomplished prior to the sintering operation becausein the final sintered form, the base materialis toohardand dense to receive and re- .tam the powder particles impinged on the surfaces by the spray gun. Also,a double sintering of the carbide would be necessary so as toob tain complete fusion and merger of the inter mediate phase with the cementing or'bind-ing material. .In the second sintering operation, there-would be a tendency to destroy thephysical characteristic and structure oftheica'rbide material accompanied by excessive anddetrimental-grain growth." r i When hot pressing is used to, form the carbide compact, painting and/or spraying of the intermediatermetal phase would be disadvantageous because the base metal would be too hard and dense to retain the particles and a disadvantageous second high'sintering temperature :would be requiredto obtain a fully dense shrunkifilmof the painted layer. f I i Thus, it is preferable to employ electroplatmg methods whena hotpressed compact is' in volved for furnishing; a uniformaand dense sur faeeishell-of;theiiintermediate phase; such as Co,

film.i-ofsthe intermediate phase'is thenfdiffused and merged withthelcementin'g metal during a subsequentheat i treatment. The subsequent I heatitreatment maybeslightly below or slightly above, the-melting point ofthe binder metal or liquid phase respectively of/the cemented carbide material; such as 2350 F.vfor tungsten-carbide cobalt eutectoid; and 2550 F. to 2650 F. for

cobalt containing dissolved titanium carbide, and

, in any. case 'substantiallybelow normalv sintering temperature toiflavoid. the detrimental," grain growth and.deterioration of physical characteriistics and; structure of vthe cementedvcarbide base imaterial. 1 i; i 1: Ii 1* I; -'I he-,extent,-of thediffusion heat treatment alsqdependsuponuthe characteristics of the camentedwcarbidesystem. In systems of great solubility-g such; as WC-Co, where-an eutectoid is;.Qrmedrxthe. treatment must be below the melting temperaturejof the low melting phase and. time relatively short. Where there is limited -SO1llbi1lty,' such as the system o ,=a-the.temp e raturecan benear the forum imea mp o edq One o f -;t l 1e preferred, manners of" furnishing the intermediatephase in connection with the hotpresstng of =-the compact is a method Where.- by aun'formshell of the intermediate phase can (be urnislied by the binder metalproper. This cantbe accomplished by carrying out the" hot vpressing operation in such a manner as to squeezeoutthe binder material during compaction so'as to. enrich the surface regions of the carbide compact at the expense :of the interior regionsl yAsan example, an 80-20 of TiC-Co mixture ca-n be hot pressed at 2900 F. at 2500 Dysai. in order to obtain a cobalt-enriched surface on the compact. The compact in such an operation issubjected to a minimum of six heat cycles ranging from 2700' F. to 3000 FE; and'the' pressure is appliedin the form of .an impact "blow. at thefmoment the peak temperature is ceramic carbide or other suitable material mold with .suiiicient space left between the surface of the skeleton bodyand the-walls of the mold cavity to; allow forthe formation of athinco'n- .tinuous surface'fi-lm of :the liquid 'infiltrant metal.

Such. s a method; of providing. .the. intermediate phase 'nthe skeleton is of; particular advantage becausel'no further heatitreatment'is required to integrally fuse and merge the surface layer of the -intermediate metal: vwith the binder metal network of the carbide skeleton. Various thicknessescf the intermediate surface phase can be obtained under controlled con-ditions depending upon themethod of producing the layer temperature of the liquid phase and-a longer process of applying the material'. If; .fOrexample, vpure chromium is .to be usedjas tha -Burr face .relement,vand-'cobaltj as the, intermediate phase layer as wellias for the binder-I912 the v carbide; a surface; layerof .0027; thickness of chi'OmiumcanbeTuSed with'a-minimum of .0031'5 thicknessof, the intermediate cobalt laye In such/an instance, thejsame thicknesses would applyif the'surface'layer were. of chromium ,-rich alloy phases with cobalt, for examplegppbalt; richsolid solution :and intermediary compounls such as-Co2Cra.-, 1

The maximum thickness shouldubelthat guarantee; somesipenetration and roots into -the binder network oftcarbider; This may-be-inthe order of .015" for the aforementioned'chromiu n surface element on the cobalt intermediate phase. -The preferred manner ;-for, deposition of gthe surface-- metals-is, by ;the vapor phase, methods, in: volving. either.u.rpurei metal; or a compound of metal that thermally decomposes :upon deposition, initiating a; metal atom, exchange process, In 'the case vof pure metals, chromium; silicon,

zirconium or aluminum, are; the most-desirable. 3

Although; pure chromium as surfacing casing is desirable for reasons of; technical simplicity and economyof; the process; the oxide ofchromium (017203) -formed .Jy hen xpos th talhigh temperature oxidizing atmospheresg lacks some stability from a mechanical standpoint and tends to. mechanically disintegrate andflal; and

' spall off "thus constantly exposing fresh-metal surfacesto the oxidizing atmospheraxl hiswould 1 eventually result in; completely Wearing through the chromiummetalsurface; Hence-metals e sulting-in, more stable oxide films such LQSQZLIITI conium,- silicon or aluminum are preferredj jf or Y very high temperature application (above 0 t v 1 If the .case formation process employs vthe previously mentioned 'mechanismpf preferred idecomposition of a: mp und th h id szo hm.

. mium; silicon, zirconiuinor aluminum,;;such as 1 chromous chloride,- chromous iodide,sili c o 7 v ride,j zirconium chloride oralumi hl are suitable for, theprocess;

. Instead of the pure metals, rit may be I advantageous and preferredto cmplo alloys ofj chromium with other metals mentioned which tend to forr mor s a le c m le o id s-1 amplcs of'alloys of chromium with elements to formgia more 'stableoxide'; areg compounds of chromium with min m; W thi qn -W th;-.Zlr

' v conium; :Wlllh aluminum and silicon; with 1alu ris-mentioned; it is desirable to have the intermediate phase continuous in thickness as well as inadherence'iand anchorage to the cementing metal network of the carbide structure. "The thickness of the intermediate phase layer preferably; is in the order of .002 to .020", the exact thickness thereof depending'lon-the type of final surfacinatmaterial t'oibe used and also on-the f S (surfacing minum; and -zirconium; -or;-with aluminum, silicon-sand zirconium, In either -case,;doubleor triple halides, such as the chlorides bromid or'tiodides: of chromium; plus alum-inn h mium plus silicon; chromium plus zirconium;

ium pl m n lu :s l cbnifc iqmiu plus aluminum -plus zirconium; or; chromium plus aluminum plussilicon l zirconium? must then ployed I 1 v It can be theorized thatlthe exchange ions I taking place-between the basemetalandthe surfacing metalby means of diffusion areas follows: i V. a j sal aeeskii telifi i a i gi le-gut where, a L

met'all may-be CnSi, Al ;'Zjr,- alloys,

B (base metal-) may be Co, Ni; alloys, I

It is..to be understood, however, thattheexact mechanism of diffusion, or. atomic interchange of the complex system may not be known. In some cases there maybe anion-exchange and in others anatomic migration, or there may be some other phenomenainvolved. 3

With the various mentioned elements, the followingwmay be takenas examples-oi thespecific .reactionsgin' relation tothe above.

Aspreviously mentioned, one of the usesfor the present invention is in conjunction. with a turbine blade for gas turbines, an example of whichis seeninFigure '1 of the drawings. In such a component, thezblade I is joined to a foot portion Illa, the foot portion [0a being insertible into a suitable aperture in the wheel of the turbine or jet engine;

Onemanner in which vapor phase impregnation or deposition of the surface metalor alloy can be: carried out is one where the component is suspended in the metal halide gasstream, one form of apparatus being illustrated in Figure 2. Furnace tube H= may be. of sillimanite or other suitable refractory material. Said tube is arranged with a gas inlet'pipe l2 and a gas outlet pipe l3; the.- component i 4 being suspended by meansof a WiIelOI rod i-5from the holding elements [6 within ztube'l I. The component I4 may be a cemented carbide refractory element with the intermediate phase surface material thereon.

The heating elements for the furnace; preferably of molybdenum or tungsten, may be divided into two sections, there being a lower element 11; connectedtotthe terminals it for the purpose of maintaining: a': predetermined temperature in the lower part of the furnace and a second heating element arrangement [9 connected to terminals 2B fonm'aintaining a, predetermined temperaturein, another portion of the'furnace. As willjbe explained hereaftenlthe temperature in tl'i'e'va'por generation portion'can be ,maintained lowenthan the temperature where the ,depositi on takes place on, the component; 1 The heating elementsjand tube mayfbe surrounded by an, insulatfiller.materialf2'l held inasuitable, gas tight housingjz- The granular metal 'materialisjlocated inside oi'tube li and mayjbe held in position'by means oflperforatedlplates 2 4 and 25', platleffljd being suitablyjpositionedby means of a :spring or other support 26;- ANihrorhe mesh workiz'lmayibe placed over the upper perforated" plate'25'as a screen to prevent solid particles from beingcarried over. Dry HCl gas is passed through inlet tube I 2' an 1:l--the gas generating zone at the lower end {of' thecylinder: The gas generating I zone includes; the=granular metal which if of chromium is kept' 'ata temperature of about 1500 F., chromous chloride;vapor-beinggenerated as the dry HCP gaspasses-over the-metal. Theunstable gas then flows into contact with the component 10 M inwhich .zone a temperature is maintained or 1800" F.1to 2.700. F..depending.on the cemented carbide system, involved. If desirable, anin'ert gas suchasargon, nitrogen or hydrogen maybe usedlasa carrier for the chromous chloride... 'It also is .possible to reverse the, flow and permit'the heavy chromous chloride vapors to descend rather than rise.

Aspreviously mentioned,.it alsois possibleto deposit other metals in a similar: mannerjfrom the vapor phasesuch as silicon,,zirconium, and aluminum. An apparatus for deposit of the pure. metal from the vapor phase is shown'fragmentarilyjin Figure. 3, the remainder of the. furnace. being similar to that illustrated in Figure'2. 'fRe'fra"ctory tube T0 may have heatinglelementsj 11'; J2 surrounding the same anda ceramic or other suitable material metal holder 13 I can be} held in place in saidtube by refractoryblocltfl. ,The metal 15 in the pot. 13 is kept in'moltenstateby the heating elements. The hydrogen or other gas passing up through theLpasSage betWeemthe pot and the walls will carry metal vapor ontoand deposit the same. on specimen 1,6. Thetempe'ra ture in thetzoneof the'pot may be maintainedat about 3100 F. and the temperature in thespecimenzone at about 275091. i .1 f, Another and preferred manner; infwhichgthe surface metal can be deposited iromtheavapor phase is by use of an impregnatedceramic carrier pack arrangement, such'asjis illustratd'inFlgure 4. In general, the component is' pla'cedin contact-witha mixture-of a suitablesceramic. such as glazed 'Alundum' or sillimanite-grainsj and chromium, silicon, aluminum and/or zirconium metal granules. The temperature is maintained between 1650 F. to 2500F-'; and'a mixturept hydrogen, and hydrogen chloride gas. passed throughthe pack which generates ajchrom'ousior other chloride vapor, which is .deposited on the surface of the component. i. As a specific example, there may be "7% hyfdifo-v gen'chloride in the gas' witha total flow 01.?500 cmii/ min. at one atmospheric pressure; Thepa'ck granulesmay be 10-20 mesh.

Referring'to Figure 4,v the refractory furnace tube 3!] has a pair of heating elements 3|l, 3Z-.o on-, nected to power sources 33 and 34, respectively. Ammeters or other suitabletinstruments 35,16 are provided in conjunction with suitable poten: tiometers '31,- 38 :'for controlling the powerinput and-thereby the 'heatingbythe' coils for heating the-furnace-tube; A suitable thermocouple" or temperature measuring; apparatus 39 and" indi cator 40 maybe provided for the purposeofindicating the temperature 'inth'e pack or'controlling the same. Insulating material 4l may be contained in casing 42 surrounding the furnace tube 301- The component which is-to havera surface deposited thereon is-indicated at-43. packed inthe granular pack, the impregnated ceramic carrier pack being supported in a suitable Nichrome suspension basket 45. The composition of the pack will be discussedhereafter. Hydro-i gen 1and H01 gas may *bei' suppliedttopipera46gin any desiredproportions, said gas being passed through a concentrated sulphuric acid absorption receptacle and calcium chloride receptacle '48 to insure that the gas is absolutely dry: Thehydrogenand HCl gas is fed through inlet 49"tothe furnace tube and'the temperature of the-furnace tube issuitably adjusted. p E

The gas passing through th' impregnated carrier pack will generate; chromousfchlofide when chromiumis used therein andwiu' deposit itfonjthe surface of the component. utlet 50 carries the gas fromthe tube into the water abisorption' receptacle then through concentrated Jsurphuric acid absorption receptacle 52 and then the calcium chloride absorption receptacle 5,3. It is evident, of course, that the connections can be varied as desired and various combinations used As mentioned before, variousmetals may be used in the place of chromium or afcombination of these metals with chromium can be used in order to provide the desirable surface deposit. Examples of methods of surfaceimpergnation to form binary, ternary, or quarternary alloys are given hereafter. First 'thefpack composition is set forth an d" then. the

procedure for carrying out the impregnation. An apparatussuch as that shown in Figure 4 is suitable for the purpose.

First wm be given examples of a chromium aluminum binary. surface impregnation by the pack gas treatment.

A.v Cr-Al.'Binary surface alloy A1. P ack composition: 50% (by weight) of 50-50 Cr- Al pulverized fused prealloy, --20 mesh granules; ,50% A1203, ,or sillimanite, 10-20 mesh.

Procedure: Dry hydrogenflow 1000 cc./min.;

HClfflow 70-100 cc./min. Passed through pack for 6-30 hr., 1740-2280 F. in alternate current, 4 reversals/hr.

A2. Pack composition: 33% of 50-50 Cr-Al prealloy, ground to --325 mesh; 17% CI'C12 crys tals; '50%+-Alz03, MgO, ZrOa or BeO, 325 -mesh. I 1 Procedure: Dry hydrogen-flow 1200 cc./min. Passed through-pack for 6-30 hr., 1740-2280 F.

A3. Pack jcomposition: 30% of 50-50 Cr-Al pre- ,alloyground to 325. mesh; CrClz crys- A chromium zirconium binary surface alloy can be deposited as follows:

tals; 5% NH4C1; 50% A1203, MgO, ZrOz or .Be0,-325 mesh. v Procedure: Dryhydrogen-flow 1200 cc./min. Passed through pack ford-30 hr., 1740-2250 F.

Next a chromium silicon binary alloy may be deposited in accordance with the following procedure: V

B. Cr-Si.-Binary" surface alloy B1. Pack composition: 50% (by weight) of Cr granules (pure,.e1ectro1.), 10-20 mesh; 50% A1203 or sillimanite granules, 10-20 mesh.

Procedure: Dry hydrogenfiow 100 cc./min., passed through liquid SiCh at 200-210" F. (boiling pt.). Gas mixture is passed through pack at 2200-2500 F. for 1 to 16 hours.

132. Pack composition: 40% (by weight) a 60-40 Cr-Si v (compound CrSi) pulverized prealloy (produced by fusing briquetted mixtures of .CrzOa plusSiC), ground to 325 mesh; 10%

"NI-RC1; 50% A1203, MgO, ZrO of B60, 325

mesh. I Procedure: 'Dry'hydrogen, .flow 1250 cc./min., "passed through pack for 6-30 hr. at 1300- 2200Ff 33. :Pack composition: 49 of 60-40 Cr-Si (compound CrSi) prealloy, 325 mesh; 49% A1203,

MgO, Zr02,-or BeO, 325 mesh; 2% iodine. Procedure: Dryhydrogen, now 1000 cc./min.,

passed through pack for 6-30 hr. at 1800-2200 F. .(as'an alternate, dry hydrogen or helium is; blended with pure chlorine gas (99%), flow @1000 cc./min.. andpassed through pack).

C. Cr-Zr.-Binary surface alloy-- 01. Pack composition: 50% of Cr granules (pure,

e1ectro1.), -10-20 mesh; 50% A1203" or sillimanite granules, 10-20 mesh. v

Procedure:

blended with a mixture of 4:1 of Cl and He, flow 750 cc./min.; passed through zirconium metal or zirconium hydride powder kept .at

' 750 F. in closed container. (As an alternate, ZrClz is first produced by passing the 4:1 Cl-He mixture over the Zr powder, then subliming the vaporized ZrClz into a powder and then passing the hydrogen over it). The hydrogenzirconium-chloride gas .mixture is passed through the pack for 2 to 30 hours at 1560- 2100 F. I

02. Pack composition: 40% of diffusion-sintered 50-50 ZrCr alloy powder pulverized, ground to 325 mesh; 10% NH4C1 50% A1203. 'MgO, ZrOz or BeO, 325 mesh.

Procedure: Dry hydrogen, flow 1250 cc./min.,

passed through pack for 6 to 30 hrs. at 1800- 2500 F.

As examples of a ternary surface alloy of chromium, aluminum and silicon, the following. procedure may be used:

D. Cr-Al-Si.Ternary surface alloypassed through pack for 6-30 hrs. at 1800- Another ternary surface I alloy of chromium. aluminum and zirconium can be deposited as follows:

E. Cr-A1-Zr.-Ternary surface alloy E1. Pack composition: 40% of 50-50 Cr-Al pulverized fused prealloy 10-20 mesh; 10% NH4C1; 50% A1203 0r sillimanite granules, -I0-20 mesh. I

Procedure; Dry hydrogen, flow 1000, cc./min.,. blended with 4:1 Cl-He gas mixture, flow 750 cc./min. passed through zirconium metalor zirconium hydride powder kept at 750 F. in a closed container, and then passed through the pack for 2 to 30 hours at 1650-2200 F. E2. Pack composition:-30% of 50-50ICr-Al pulverized fused prealloy, 325 mesh: 15% ZrClz powder; 5% NI-I401; 50% A1203. MgO, ZrOz or BeO, -325 mesh.

Procedure:

I. ZIC12 produced by passing 4:1 Cl-Hetgas. mixture, flow 500-1000 cc./min. over zirconium metal or hydride powder at 750 F., sublimation of the vaporized ZrClz into a-powder.

II. Dry hydrogen, flow 1000 cc./min., passed glgggugh the pack for 2 to .30 hours at 1800- Dry hydrogen, 'flow moo ed/mm,

513 quaternary-surface allow- 'contaihingechroe miunr,aluminum,- silicon ,jand zirconium: may 'be deposited accordingto the followingimethods' .i E:.CbAl-SigZiifiQuaternary -surface.alloy F1. Pack composition: 40% of 40-40{201Cr sieAi pulverizedfused qprealloy, 10-20 mesh; 10% NH4C1; 50% A1203 or sillimanite granules, -10-20 meshr: Procedure: Dry hydrogen,, fiow 1QO0. cc./min., blended with 4:1CI He'gas tyre; flow 750 cc./min., passed through zirconium metal or zirconium hydride powder Kept as 750 F. in ,closed;-container, and them-passed through the pack for ,2 to 30 hours at;;1 6 50-2000.-

r'gjr rack composition: 30% of 40-40-2 Cr-fSi-Al "1 pulverized fused-prealloy," -325 meshg 15% AhQa, Mao.

ZrGla' powdery-% NH4C1;" '50 ZrOi-"or BeO, ---32-5--mesh.

B e r r 1. 1

I; zrcu produced by passing 4 1 Cl-He 'g'as mixture,=flow 500-1000--cc.=/-mini over zirconium metal or hydride powder-at "750 F. sublimation "of the -vaporized- ZrClz, into a powder.

V II; Dry hydrogen, flow-1000 cc./min;, passed through thapack for- 2 to? -30 hours at 1800 2500 F.

An illustration of the invention based on an X250 photomicrograph is seen in Figure 5 wherein the chromium deposited surface phase is indicated at 60 and the tungsten carbide body cemented with 20% of a binder of cobalt at 6!. The intermediate phases are seen at 62 and 62A of cobalt and cobalt chromium alloy formed by diffusion. The cobalt chromium alloy contains eutectic indicated, for example, at 65, and the outer surface of the specimen is shown at 63. The cobalt chromium alloy also penetrates into the tungsten carbide base such as may be seen, for example, at 64. At least a portion of the cobalt and chromium form an eutectic in the intermediate phase and where penetration takes place into the tungsten carbide base.

A schematic representation is seen in Figure 6 wherein the refractory metal carbide grains are indicated at 10 and the cementing metal or alloy at 66. The intermediate phase of the same material as the binder is shown at 61 and the deposited surface metal or alloy is indicated at 68. In the process, an eutectic of the cobalt chromium metals will be formed and may travel or migrate into the surface layers such as indicated at E9. The eutectic also is indicated at 69A as penetrating into the cemented tungsten carbide base.

As previously mentioned, a salt bath chromizing or other depositing process might be used wherein the componentis brought into contact, with a stable halogen salt as a constituent of a "molten bath such as CrClz, the temperature in i such an instance being maintained at about 2000 In such a process, the free chromium would be made available at.

F.-2500 F. for several hours.

the previously deposited and integrally merged intermediate metal surface of the component through the exchange reaction:

CrClz-l-Fe, o0, ni neoi oocl NiCIa-I-Cr Other metals such as silicon, zirconium, or aluminum, or alloys thereof with chromium,may be similarly deposited. It is also possible'to de- A tungsten carbide powder were. powder :size. of from to '7 micron cansb'e mixedilwitlr'13% by weight cobalt of -325 meshand' the" mixture hot pressed at approximately 2650:F;= under a pressure of about 2 tons per square inch' in a procedure involving alternating heating and pressing-cycles as mentioned hitherto.- Theresuiting body can be observed to possess asur faceregion enriched in the cobalt bindermetal; In-add-ition; anintermediate phase-of nickel then can be electroplated thereon-with a thickness of *about 002:.005 thickness. 'Thespecimen then canhe-placed in an apparatus similar to that seen in "Figure-.4 of the drawings The pack which can be-usedf is an equi-volume-mixtureof"10-'- l6 mesh electrolytic chromium modules and white glazed Alundumgrains The furnace tlien carr have hydrogen chloride and hydrogen gas passed therethrough in the ratioof 840% for thirty hours, the furnacebeing maintained at "between 1830 F. and 2011) F. the 'libw rate being1000 'cc./-min.- F i L Alsoyatungstencarbide-cobaltWoodymad thesame-mannen as =that gjust c l escribed can be additionally-plated w-ith cobalt and then placed 7 of the intermediate casing layer of the composite body and the surface case also can be performed in various manners. The term metal means a single metal or an alloy. Also, the precise mechanism of the deposition and bonding is not necessarily that of an atom exchange, but may be some other process, such as a thermal decomposition of the compound liberating metal ions followed by atomic migration, or may be some other phenomena. Details of carrying out the process and the apparatus involved can be varied from those shown without departing from the spirit of the invention, except as defined in the appended claims.

What is claimed is: i 1. The method of producing composite bodies adapted to withstand corrosion at a high tem-- perature comprising compacting said composite bodies from a refractory metal carbide powder posit these other metals or alloys directly in the vapor form when the conditions bearing on the vapor pressure characteristics are correct for deposition.

selected from a group consisting of titanium car-g bide, molybdenum carbide, tungsten carbide and zirconium carbidepowder, cementing the said bodies with a metal selected from a group consisting of iron, nickel and cobalt, applying to the surface of said cemented bodies an intermediate layer of the metals used for the cementing step, covering said intermediate metal layer with a surface coating of a substance selected from a group composed of chromium, zirconium, aluminum; silicon and their halides and thermally merging said intermediate and said surface layers into a bond therebetween and with said cemented body.

2. In a method according to claim 1, the step of using the same metal for the cementing of said compositebodies and for the formation 1, of

the intermediate" layer.

- 3. In a method according to claim 1, the step v of compacting the composite body from a titanicarbide powder, cementing the same with a metal selected from the group consisting of iron, cobalt, nickel, applying to the said cemented body an intermediate cobalt layer and covering the samewith a surface layer of a substance selected from a group consisting of chromiumzirconium,

aluminum and. silicon.

4;..In a method according to claim 1, the step of compacting the composite body from a titanium carbide powder, cementing the samewith a metal selected-from the group consisting of iron, cobalt, nickel, applying to the said cemented body an intermediate nickel layer and covering the same -with a surface layer oi' asubstance selected from a group consisting of chromium, zirconium, aluminum and silicon. 5. A composite body which is corrosion resistant; at a, high temperature consistingof a refractory' metal powder selected vfrom the group consisting of titanium carbide, molybdenum, carbide, tungsten carbide and zirconium carbide powders andbeing cemented by a metal selected from a group consistingof iron, nickel and cobalt,

said body being coated with an intermediate layer of the'metal's used for thecementingstep and.

being surfacev coated with a substance selected from a group'compose'dofchromium, zirconium, aluminum and silicon, the saidbody being me suriace' la'yen.

I 'CLAUS G.GOETZE l' 1:

; REFERENCES CITED file I of this patent:

. UNITED STATES PATENTS- Number Scherer Oct. 17,; 1950 tegrallyj-united' with the intermediate and" the y The following references areof record 

1. THE METHOD OF PRODUCING COMPOSITE BODIES ADAPTED TO WITHSTAND CORROSION AT A HIGH TEMPERATURE COMPRISING COMPACTING SAID COMPOSITE BODIES FROM A REFRACTORY METAL CARBIDE POWDER SELECTED FROM A GROUP CONSISTING OF TITANIUM CARBIDE, MOLYBDENUM CARBIDE, TUNGSTEN CARBIDE AND ZIRCONIUM CARBIDE POWDER, CEMENTING THE SAID BODIES WITH A METAL SELECTED FROM A GROUP CONSISTING OF IRON, NICKEL AND COBALT, APPLYING TO THE SURFACE OF SAID CEMENTED BODIES AN INTERMEDIATE LAYER OF THE METALS USED FOR THE CEMENTING STEP, COVERING SAID INTERMEDIATE METAL LAYER WITH A SURFACE COATING OF A SUBSTANCE SELECTED FROM A GROUP COMPOSED OF CHROMIUM, ZIRCONIUM, ALUMINUM, SILICON AND THEIR HALIDES AND THERMALLY MERGING SAID INTERMEDIATE AND SAID SURFACE LAYERS INTO A BOND THEREBETWEEN AND WITH SAID CEMENTED BODY.
 5. A COMPOSITE BODY WHICH IS CORROSION RESISTAND AT A HIGH TEMPERATURE CONSISTING OF A REFRACTORY METAL POWDER SELECTED FROM THE GROUP CONSISTING OF TITANIUM CARBIDE, MOLYBDENUM, CARBIDE TUNGSTEN CARBIDE AND ZIRCONIUM CARBIDE POWDERS AND BEING CEMENTED BY A METAL SELECTED FROM A GROUP CONSISTING OF IRON, NICKEL AND COBALT, SAID BODY BEING COATED WITH AN INTERMEDIATE LAYER OF THE METALS USED FOR THE CEMENTING STEP AND BEING SURFACE COATED WITH A SUBSTANCE SELECTED FROM A GROUP COMPOSED OF CHROMIUM, ZIRCONIUM, ALUMINUM AND SILICON, THE SAID BODY BEING INTEGRALLY UNITED WIT THE INTERMEDIATE AND THE SURFACE LAYER. 